This invention relates to a surge diverter with several spark-quenching gaps, comprising voltage-controlled discharge resistors connected in series with these gaps and voltage-controlled control-resistors each of which is connected in parallel either with a spark-quenching gap or with the serial unit formed by a spark-quenching gap and a discharge resistor mounted in series. The prior art, as shown for instance in CH-Pat. No. 312 772, provides surge diverters with voltage-controlled resistors mounted in parallel either with each spark-quenching gap, or with the serial unit formed by a spark-quenching gap and a voltage-controlled discharge resistor mounted in series, in order to obtain a uniform voltage distribution.
The voltage at the leads of a voltage-dependant resistor is given by the formula EQU U=kI.alpha.
where k and .alpha. are constants. Resistors with a greater .alpha. have a steeper current-voltage characteristic.
A drawback of the arrestor mentioned in Swiss Pat. No. 314 772 is that the control resistors must carry a comparatively high current at the rated voltage, in order to suppress the influence of the stray capacitance. These control resistances therefore are comparatively bulky and consequently expensive.
The German published patent application No. 1.192.733 also describes an arrestor of the above type, in which the voltage-dependent resistors have characteristics of different steepness and exhibit about the same resistance at the rated voltage. However, the manufacture of such resistors offers considerable difficulty.